Electrochemical device

ABSTRACT

An electrochemical device is provided, comprising a source contact connected to a first antenna pad, a drain contact connected to a second antenna pad, at least one gate electrode, an electrochemically active element arranged between, and in direct electrical contact with, the source and drain contacts, which electrochemically active element comprises a transistor channel and is of a material comprising an organic material having the ability of electrochemically altering its conductivity through change of redox state thereof, and a solidified electrolyte in direct electrical contact with the electrochemically active element and the at least one gate electrode and interposed between them in such a way that electron flow between the electrochemically active element and the gate electrode(s) is prevented. In the device, flow of electrons between source contact and drain contact is controllable by means of a voltage applied to the gate electrode(s).

FIELD OF THE INVENTION

[0001] The present invention relates to radio frequency identificationtags, and in particular to a radio frequency identification tag that ismodulated by an electrochemical device. In particular, the presentinvention relates to printable, electrostatic antennas together withprintable electrochemical transistor devices, based on conductingorganic and/or inorganic materials.

BACKGROUND OF THE INVENTION

[0002] Remotely read identification tags have a wide range of differentapplications and uses (see for example RFID HANDBOOK “Radio-FrequencyIdentification Fundamentals and Applications” by Klaus Finkenzeller,John Wiley & Sons Ltd, Baffins Lane, Chichester, West Sussex, P019 1UD,England, ISBN 0 471 98851 0). One of the technologies is thecapacitively coupled identification system such as Motorola's BiStatix™technology. In these systems the smart part of the tag is in a siliconbased integrated circuit placed in proximity to the antenna unit(capacitive coupled antenna). This chip together with the capacitevelycoupled antenna unit is used to transmit a signal, usually anidentification code. The connection between the integrated circuit andthe antenna plates (usually two) may be via a transistor inside thecircuit. The signal from the integrated circuit is, via the transistor,used for modulating the antenna characteristics in such a fashion thatthe receiver can recognise the signal and detect an ID code.

[0003] Semi-conducting and conducting organic materials, both polymersand molecules, have successfully been included in a large range ofelectronic devices, e g electrochemical devices, for instance as dynamiccolorants in smart windows and in polymer batteries. Reversible dopingand de-doping involving mobile ions switches the material betweendifferent redox states.

[0004] Use has been made of semi-conducting polymers for the realisationof field effect transistor (FET) devices. The transistor channel ofthese devices comprises the semi-conducting polymer in question, andtheir function is based on changes in charge carrier characteristics inthe semi-conducting polymer, caused by an externally applied electricfield. In such transistors, the polymer is used as a traditionalsemiconductor, in that the electric field merely redistributes chargeswithin the polymer material. One such transistor has been realised,which is adapted for miniaturisation and can be used for the productionof integrated circuits consisting entirely of polymer material (PCTpublication WO99/10939). A stack of sandwiched layers is described, witheither a top-gate or a bottom-gate structure. A transistor device with asimilar architecture, also using a polymer as semi-conducting materialin the channel of the transistor, is described in the European patentapplication EP 1041653.

[0005] Another type of transistor device based on organic materialsutilises electrochemical redox reactions in the organic material. Thesedevices comprise an electrolyte and a conducting polymer that can beswitched between an oxidised and a reduced state. One of these oxidationstates then corresponds to low, preferably zero, conductivity in thematerial, whereas the other oxidation state corresponds to a highconductivity relative to the first state. Electrochemical transistordevices have been used as sensors, e g for detection of oxidant in asolution (see, for review, Baughman and Shacklette, Proceedings of theSixth Europhysics Industrial Workshop (1990), p 47-61). Furthermore, atransistor of the electrochemical type is reported in Rani et al, JSolid State Electrochem (1998), vol 2, p 99-101. The gate electrodearchitecture in this prior art transistor is shown in FIG. 1 of thisreference.

[0006] Problems with capacitively coupled identification devices in theprior art include that they are difficult and expensive (>0.50 USD) tomanufacture. In particular, the chip part of the identification unit islimiting the capability to mass-produce the tags to lower prices.Furthermore, materials used in the chips of prior art devices sufferfrom a lack of environmental friendliness, processability and economicproduction possibilities. Consequently, there is a need for new andimproved identification circuitry with a simplified antenna-logicconnection.

SUMMARY OF THE INVENTION

[0007] One of the objects of the present invention is then to meet thisdemand, by developing the art of capacitively coupled identificationdevices with an active antenna logic connection, and by providing adevice with handling, production, disposal and other characteristicssuperior to those of the prior art.

[0008] Another object of the present invention is to provide acapacitively coupled identification device with an active antenna logicconnection, which can be deposited on a large range of different rigidor flexible substrates by conventional printing methods.

[0009] Yet another object of the present invention is to provide anenvironmentally safe, capacitively coupled identification device with anactive antenna logic connection so that the disposal of the device,along with any support onto which it has been deposited, does not giverise to handling problems, and so that no safety restrictions have to beimposed on the use of the device.

[0010] Still another object of the present invention is to make possiblenew applications of conducting organic materials, using severaldifferent properties of such materials in combination.

[0011] A further object of the invention is to provide processes for theproduction of such devices, which processes utilise conventionalprinting methods or other deposition techniques that are well known,relatively inexpensive and easily scaled up.

[0012] The aforementioned objects are met by capacitively coupledidentification devices with an active antenna logic connection, asdefined in the independent claims. Specific embodiments of the inventionare defined in the dependent claims. In addition, the present inventionhas other advantages and features apparent from the detailed descriptionbelow.

[0013] Thus, a supported or self-supporting electrochemical transmitterdevice is provided, which comprises:

[0014] (i) an electrochemical transistor member having

[0015] a source contact,

[0016] a drain contact,

[0017] at least one gate electrode,

[0018] an electrochemically active element arranged between, and indirect electrical contact with, the source and drain contacts, whichelectrochemically active element comprises a transistor channel and isof a material comprising an organic material having the ability ofelectrochemically altering its conductivity through change of redoxstate thereof, and

[0019] a solidified electrolyte in direct electrical contact with theelectrochemically active element and said at least one gate electrodeand interposed between them in such a way that electron flow between theelectrochemically active element and said gate electrode(s) isprevented,

[0020] whereby flow of electrons between source contact and draincontact is controllable by means of a voltage applied to said gateelectrode(s); and

[0021] (ii) an antenna member having a first antenna pad and a secondantenna pad, wherein the source of the transistor member is in directelectrical contact with the first antenna pad and the drain of thetransistor member is in direct electrical contact with the secondantenna pad, such that the voltage applied to the gate electrode(s) cancontrol the flow of electrons between the first and the second pad ofthe antenna member and thereby alter the frequency response of thetransmitter device.

[0022] The architecture of the transmitter device according to theinvention is advantageous in that it makes possible the realisation of alayered transmitter device with only a few layers, having for exampleone patterned layer of material comprising a conducting organicmaterial, which layer comprises antenna pad(s), source and draincontacts and gate electrode(s), as well as the electrochemically activeelement. The antenna pad(s), source and drain contacts and theelectrochemically active element are then preferably formed by onecontinuous piece of said material. The antenna pad(s), source and draincontacts could alternatively be formed from another electricallyconducting material, such as a silver- or coal-based material, in directelectrical contact with the electrochemically active element. The gateelectrode (s) may also be of another electrically conducting material.To provide for the necessary electrochemical reactions, whereby theconductivity in the active element is changed and hence the electricalconnection (resistance) between the antenna pads is modulated, asolidified electrolyte is arranged so that it is in direct electricalcontact with both the active element and the gate electrode(s).

[0023] It is to be understood, that the term transmitter device includesfor example transponders and RF-ID (Radio Frequency Identification)tags.

[0024] In a preferred embodiment, the antenna pad(s), source and draincontacts and gate electrode(s), as well as the active element, are allarranged to lie in a common plane, further simplifying production of thedevice by ordinary printing methods. Thus, the transmitter deviceaccording to this embodiment of the invention uses a lateral devicearchitecture. A layer of solidified electrolyte can advantageously bedeposited so that it covers, at least partly, the gate electrode(s) aswell as covering the electrochemically active element. This layer ofsolidified electrolyte may be continuous or interrupted, dependingpartly on which of two main types of transistor architectures is to berealised between the antenna pads (see below).

[0025] The electrochemical transmitter device according to the inventionallows for control of electron flow between source and drain contactsand hence between the two antenna pads of the antenna member of thetransmitter. The conductivity of the transistor channel of theelectrochemically active element can be modified, through altering ofthe redox state of the organic material therein and thereby altering theantenna characteristics. This is achieved by application of a voltage tothe gate electrode(s), which generates an electric field in theelectrolyte. In the contact area between electrolyte andelectrochemically active element, electrochemical redox reactions takeplace, which change the conductivity of the organic material. Either theorganic material in the transistor channel is modified from a conductingstate to a non-conducting state as a result of said redox reactions, orit is modified from a non-conducting to a conducting state. If applyinga high enough voltage to the gate electrode(s), the electrochemicallyactive element might in some cases experience an irreversible redoxreaction which permanently affects the conductivty of the element. Insome cases, it is even possible to render the element essentiallynon-conducting. This is the case for example if the electrochemicallyactive element is made of PEDOT:PSS, and results in the antenna pads (orthe antenna pad and ground) being permanently insulated from each other.Thus, the antenna characteristics of such a device is permanentlychanged giving the device a permanent memory function. Consequently,such a device can be used as a permanently programmable logic element,for example defining a logic zero if the active element is renderednon-conducting and a logic one if it is not rendered non-conducting.Once programmed, the binary information can be read out remotely by asuitable read out device detecting the antenna characteristics.

[0026] Depending on the precise patterning of the conducting organicmaterial and the electrolyte, the electrochemical transistor member ofthe transmitter according to the invention can either be of a bi-stableor a dynamic type. In the bi-stable transistor embodiment, a voltageapplied to the gate electrode(s) leads to a change in conductivity inthe transistor channel that is maintained when the external circuit isbroken, i e when the applied voltage is removed. The electrochemicalreactions induced by the applied voltage can not be reversed, since theelectrochemically active element and the gate electrode(s) are not indirect electrical contact with each other, but separated by electrolyte.In this embodiment, the transistor channel can be switched betweennon-conducting and conducting states using only small, transient gatevoltages. The bi-stable transistor can be kept in an induced redox statefor days, and, in the most preferred, ideal case, indefinitely. Thedevice is thus provided with a permanent memory function which, contraryto the above-mentioned irreversible redox reaction, is re-programmable.

[0027] Thus, the bi-stable transistor embodiment of the presentinvention offers a memory function, in that it is possible to switch iton or off using only a short voltage pulse applied to the gateelectrode. The transistor stays in the conducting or non-conductingredox state even after the applied voltage has been removed. A furtheradvantage with such bi-stable transistors is that close to zero-poweroperation is made possible, since the short voltage pulses applied tothe gate need not be larger than a fraction of the gate voltages neededfor operation of a corresponding dynamic device.

[0028] In the dynamic transistor embodiment, the change in the redoxstate of the material is reversed spontaneously upon withdrawal of thegate voltage. This reversal is obtained through the provision of a redoxsink volume adjacent to the transistor channel in the electrochemicallyactive element. Also, a second gate electrode is provided, and arrangedso that the two gate electrodes are positioned on either side of theelectrochemically active element, one closer to the transistor channel,and the other closer to the redox sink volume. Both gate electrodes areseparated from the electrochemically active element by electrolyte.Application of a voltage between the two gate electrodes results in theelectrochemically active element being polarised, whereby redoxreactions take place in which the organic material in the transistorchannel is reduced while the organic material in the redox sink volumeis oxidised, or vice versa, and hence the antenna response is modulated.Since the transistor channel and the redox sink volume are in directelectrical contact with each other, withdrawal of gate voltage leads toa spontaneous reversal of the redox reactions, so that the initialconductivity of the transistor channel is re-established.

[0029] The electrochemical transmitter device according to the inventionis also particularly advantageous in that it can be easily realised on asupport, such as polymer film or paper. Thus, the different componentscan be deposited on the support by means of conventional printingtechniques such as screen printing, offset printing, ink-jet printingand flexographic printing, or coating techniques such as knife coating,doctor blade coating, extrusion coating and curtain coating, such asdescribed in “Modern Coating and Drying Technology” (1992), eds E DCohen and E B Gutoff, VCH Publishers Inc, New York, N.Y., USA. In thoseembodiments of the invention that utilise a conducting polymer as theorganic material (see below for materials specifications), this materialcan also be deposited through in situ polymerisation by methods such aselectropolymerisation, UV-polymerisation, thermal polymerisation andchemical polymerisation. As an alternative to these additive techniquesfor patterning of the components, it is also possible to use subtractivetechniques, such as local destruction of material through chemical orgas etching, by mechanical means such as scratching, scoring, scrapingor milling, or by any other subtractive methods known in the art. Anaspect of the invention provides such processes for the manufacture ofan electrochemical transmitter device from the materials specifiedherein.

[0030] According to a preferred embodiment of the invention, theelectrochemical transistor member of the transmitter device isencapsulated, in part or entirely, for protection of the device. Theencapsulation retains any solvent needed for e g the solidifiedelectrolyte to function, and also keeps oxygen from disturbing theelectrochemical reactions in the device. Encapsulation can be achievedthrough liquid phase processes. Thus, a liquid phase polymer or organicmonomer can be deposited on the device using methods such asspray-coating, dip-coating or any of the conventional printingtechniques listed above. After deposition, the encapsulant can behardened for example by ultraviolet or infrared irradiation, by solventevaporation, by cooling or through the use of a two-component systemsuch as an epoxy glue, where the components are mixed together directlyprior to deposition. Alternatively, the encapsulation is achievedthrough lamination of a solid film onto the electrochemical transistormember of the transmitter device. In preferred embodiments of theinvention, in which the components of the electrochemical transistormember of the transmitter device are arranged on a support, this supportcan function as the bottom encapsulant. In this case encapsulation ismade more convenient in that only the top of the sheet needs to becovered with liquid phase encapsulant or laminated with solid film.

[0031] In another preferred embodiment, such a printable transmitterdevice is provided, which is constructed from the same materials as asensor. In this case, the sensor is used to modulate the characteristicsof the transistor member of the device according to the invention. It isthen possible to realise printable sensor memory circuitry for atransmitter device on the same support, using the same materials anddeposition techniques as for the transmitting unit itself. An ensemblecomprising a printable sensor memory and a transmitter device can thenbe printed, all at the same time, on a support.

[0032] The antenna member of the present invention may be, any knowntype. Basically, the antenna member is a dipole element, wherein the twoantenna pads operate as radiating portions. By controlling the electronflow (i.e. the resistance) between the two pads, the frequency, power,phase and/or other parameters of the radio frequency response may bealtered. The state of the transistor, and hence of the characteristicsdetermining the state of the transistor, may be read out remotely by asimilar antenna structure. Depending on which parameters of the radiofrequency response that are altered, different types of remote read outstructures can be used. A read-out device may for example comprise anantenna, identical or similar to the antenna in the device according tothe invention, which is brought in proximity with the inventive device.A radio frequency emitted by the read-out device is reflected from theantenna member of the electrochemical device according to the presentinvention, and by virtue of the frequency response being dependent uponthe state of the transistor member, information may be extracted.

[0033] The invention will now be further described with reference tospecific embodiments thereof and to specific materials. This detaileddescription is intended for purposes of exemplification, not forlimitation in any way of the scope of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The following detailed description will be more thoroughlyunderstood when read in conjunction with the accompanying drawings, onwhich

[0035] FIGS. 1A-C are schematic views of a structure of one embodimentof a transmitter device according to the invention, wherein the antennamember is connected to a bi-stable transistor, showing (A) a top viewand (B) a cross-section along I-I in A, and (C) an alternativeembodiment wherein the drain of the transistor member is connected toground;

[0036]FIG. 2A-C are schematic views of a structure of a transmitterdevice according to the invention, wherein the antenna member isconnected to a dynamic transistor, showing (A) a top view and (B) across-section along I-I in A, and (C) an alternative embodiment whereinthe drain of the transistor member is connected to ground;

[0037]FIG. 3A-C are schematic views of a structure of another embodimentof a transmitter device according to the invention, wherein the antennamember is connected to a bi-stable transistor, showing (A) a top viewand (B) a cross-section along I-I in A, and (C) an alternativeembodiment wherein the drain of the transistor member is connected toground;

[0038]FIGS. 4 and 5 show the gate voltage dependency on drain/sourcevoltage for a transistor member in accordance with the presentinvention;

[0039]FIG. 6 shows schematically an electrochemical device according tothe invention, along with a capacitively coupled read-out device;

[0040]FIG. 7 shows schematically the capacitively coupled read-outdevice of FIG. 6, in a situation where the drain of the transistormember is coupled to ground, rather than to an antenna pad;

[0041]FIG. 8 shows the characteristic changes in reader signal whenmeasuring on a device in connection with a bi-stable transistor as shownin FIG. 1; and

[0042]FIG. 9 shows the characteristic changes in reader signal whenmeasuring on a device in connection with a dynamic transistor as shownin FIG. 2.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0043] Definitions

[0044] Bi-stable electrochemical transistor: an electrochemicaltransistor device in which the transistor channel retains its redoxstate (and hence its conductivity characteristics) when the gate voltageis removed.

[0045] Dynamic electrochemical transistor: an electrochemical transistordevice in which the transistor channel spontaneously returns to itsinitial redox state (and hence to its initial conductivitycharacteristics) when the gate voltage is removed.

[0046] Source contact: An electrical contact that provides chargecarriers to a transistor channel. According to the present invention,the source contact is connected to one of the pads of a capacitivelycoupled device (i.e. the first pad of the antenna member).

[0047] Drain contact: An electrical contact that accepts charge carriersfrom a transistor channel. According to the present invention, the draincontact is connected to one of the plates of an capacitive coupleddevice or coupled to ground (i.e. the second pad of the antenna memberor to ground).

[0048] Gate electrode: an electrical contact of which any fraction ofthe surface area is in direct electrical contact with solidifiedelectrolyte, and therefore in ionic contact with the electrochemicallyactive element.

[0049] Electrochemically active element: an “electrochemically activeelement” according to the present invention, is a piece of a materialcomprising an organic material having a conductivity that can beelectrochemically altered through changing of the redox state of saidorganic material. The electrochemically active element is in ioniccontact with at least one gate electrode via a solidified electrolyte.The electrochemically active element may furthermore be integrated witheach of the source and drain contacts individually or with both of them,being composed of the same or different materials. The electrochemicallyactive element in the electrochemical transistor devices of theinvention comprises a transistor channel, and may furthermore comprise aredox sink volume.

[0050] Transistor channel: the “transistor channel” of theelectrochemically active element establishes electrical, contact betweensource and drain contacts.

[0051] Redox sink volume: in certain embodiments of the invention, theelectrochemically active element further comprises a “redox sinkvolume”. This is a part of the electrochemically active element adjacentto and in direct electrical contact with the transistor channel, whichcan provide or accept electrons to or from the transistor channel. Thus,any redox reactions within the transistor channel are complemented byopposing reactions within the redox sink volume.

[0052] Redox state: when reference is made to changes in the “redoxstate” of the electrochemically active element, this is intended toinclude cases where the organic material in the electrochemically activeelement is either oxidised or reduced, as well as cases where there is aredistribution of charges within the electrochemically active element,so that one end (e g the transistor channel) is reduced and the otherend (e g the redox sink volume) is oxidised. In the latter case, theelectrochemically active element as a whole retains its overall redoxstate, but its redox state has nevertheless been changed according tothe definition used herein, due to the internal redistribution of chargecarriers.

[0053] Direct electrical contact: Direct physical contact (commoninterface) between two phases (for example electrode and electrolyte)that allows for the exchange of charges through the interface. Chargeexchange through the interface can comprise transfer of electronsbetween electrically conducting phases, transfer of ions betweenionically conducting phases, or conversion between electronic currentand ionic current by means of electrochemistry at an interface betweenfor example electrode and electrolyte or electrolyte andelectrochemically active element, or by occurrence of capacitivecurrents due to the charging of the Helmholtz layer at such aninterface.

[0054] Solidified electrolyte: for the purposes of the invention,“solidified electrolyte” means an electrolyte, which at the temperaturesat which it is used is sufficiently rigid that particles/flakes in thebulk therein are substantially immobilised by the highviscosity/rigidity of the electrolyte and that it doesn't flow or leak.In the preferred case, such an electrolyte has the proper rheologicalproperties to allow for the ready application of this material on asupport in an integral sheet or in a pattern, for example byconventional printing methods. After deposition, the electrolyteformulation should solidify upon evaporation of solvent or because of achemical cross-linking reaction, brought about by additional chemicalreagents or by physical effect, such as irradiation by ultraviolet,infrared or microwave radiation, cooling or any other such. Thesolidified electrolyte preferably comprises an aqueous or organicsolvent-containing gel, such as gelatine or a polymeric gel. However,solid polymeric electrolytes are also contemplated and fall within thescope of the present invention. Furthermore, the definition alsoencompasses liquid electrolyte solutions soaked into, or in any otherway hosted by, an appropriate matrix material, such as a paper, a fabricor a porous polymer. In some embodiments of the invention, this materialis in fact the support upon which the electrochemical transistor deviceis arranged, so that the support forms an integral part of the operationof the device.

[0055] Materials

[0056] Preferably, the antenna pad(s) are made from a printable orprinting process compatible, conducting material. It is preferred thatthis conducting material is a material that can be handled in a“roll-to-roll” process, such as printing and lamination etc. Theconducting material is preferably a metallic foil such as aluminium,brass or copper, or is chosen from the group of conducting inksavailable such as silver-, carbon-inks or a conducting organic and/orpolymeric coating or ink.

[0057] The organic material for use in the antenna member of the presentinvention preferably comprises a polymer which is electricallyconducting in at least one oxidation state and optionally furthercomprises a polyanion compound. Conductive polymers for use in theelectrochemical transistor member of the invention are preferablyselected from the group consisting of polythiophenes, polypyrroles,polyanilines, polyisothianaphthalenes, polyphenylene vinylenes andcopolymers thereof such as described by J C Gustafsson et al in SolidState Ionics, 69, 145-152 (1994); Handbook of Oligo- and Polythiophenes,Ch 10.8, Ed D Fichou, Wiley-VCH, Weinhem (1999); by P Schottland et alin Macromolecules, 33, 7051-7061 (2000); Technology Map ConductivePolymers, SRI Consulting (1999); by M Onoda in Journal of theElectrochemical Society, 141, 338-341 (1994); by M Chandrasekar inConducting Polymers, Fundamentals and Applications, a PracticalApproach, Kluwer Academic Publishers, Boston 1999); and by A J Epsteinet al in Macromol Chem, Macromol Symp, 51, 217-234 (1991). In anespecially preferred embodiment, the organic material is a polymer orcopolymer of a 3,4-dialkoxythiophene, in which said two alkoxy groupsmay be the same or different or together represent an optionallysubstituted oxy-alkylene-oxy bridge. In the most preferred embodiment,the polymer is a polymer or copolymer of a 3,4-dialkoxythiopheneselected from the group consisting of poly3,4-methylenedioxythiophene),poly3,4-methylenedioxythiophene) derivatives,poly3,4-ethylenedioxythiophene), poly3,4-ethylenedioxythiophene)derivatives, poly3,4-propylenedioxythiophene),poly3,4-propylenedioxythiophene) derivatives,poly3,4-butylenedioxythiophene), poly3,4-butylenedioxythiophene)derivatives, and copolymers therewith. The polyanion compound is thenpreferably polystyrene sulphonate).

[0058] Preferably, the solidified electrolyte, used in the transistormember of the present invention, comprises a binder. It is preferredthat this binder have gelling properties. The binder is preferablyselected from the group consisting of gelatine, a gelatine derivative,polyacrylic acid, polymethacrylic acid, poly(vinylpyrrolidone),polysaccharides, polyacrylamides, polyurethanes, polypropylene oxides,polyethylene oxides, poly(styrene sulphonic acid) and poly(vinylalcohol) and salts and copolymers thereof; and may optionally becross-linked. The solidified electrolyte preferably further comprises anionic salt, preferably magnesium sulphate if the binder employed isgelatine. The solidified electrolyte preferably further contains ahygroscopic salt such as magnesium chloride to maintain the watercontent therein.

[0059] The organic material for use in the present invention preferablycomprises a polymer which is electrically conducting in at least oneoxidation state and optionally further comprises a polyanion compound.Conductive polymers for use in the electrochemical transistor device ofthe invention are preferably selected from the group consisting ofpolythiophenes, polypyrroles, polyanilines, polyisothianaphthalenes,polyphenylene vinylenes and copolymers thereof such as described by J CGustafsson et al in Solid State Ionics, 69, 145-152 (1994); Handbook ofOligo- and Polythiophenes, Ch 10.8, Ed D Fichou, Wiley-VCH, Weinhem(1999); by P Schottland et al in Macromolecules, 33, 7051-7061 (2000);Technology Map Conductive Polymers, SRI Consulting (1999); by M Onoda inJournal of the Electrochemical Society, 141, 338-341 (1994); by MChandrasekar in Conducting Polymers, Fundamentals and Applications, aPractical Approach, Kluwer Academic Publishers, Boston (1999); and by AJ Epstein et al in Macromol Chem, Macromol Symp, 51, 217-234 (1991). Inan especially preferred embodiment, the organic material is a polymer orcopolymer of a 3,4-dialkoxythiophene, in which said two alkoxy groupsmay be the same or different or together represent an optionallysubstituted oxy-alkylene-oxy bridge. In the most preferred embodiment,the polymer is a polymer or copolymer of a 3,4-dialkoxythiopheneselected from the group consisting of poly(3,4-methylenedioxythiophene),poly(3,4-methylenedioxythiophene) derivatives,poly(3,4-ethylenedioxythiophene), poly(3,4-ethylenedioxythiophene)derivatives, poly(3,4-propylenedioxythiophene),poly(3,4-propylenedioxythiophene) derivatives,poly(3,4-butylenedioxythiophene), poly(3,4-butylenedioxythiophene)derivatives, and copolymers therewith. The polyanion compound is thenpreferably poly(styrene sulphonate).

[0060] The support in some embodiments of the transmitter deviceaccording to the present invention is preferably selected from the groupconsisting of polyethylene terephthalate; polyethylene naphthalenedicarboxylate; polyethylene; polypropylene; paper; coated paper, e.g.coated with resins, polyethylene, or polypropylene; paper laminates;paperboard; corrugated board; glass and polycarbonate.

[0061] Principal Device Architectures

[0062] The different transistors possible to incorporate into thecapacitive coupled antenna structures:

[0063] By patterning of the organic material of the electrochemicallyactive element and of the contacts, electrode(s) and electrolyte indifferent ways, two main types of electrochemical transistor devices canbe realised. Electrochemical devices according to the invention, basedon these main types, namely bi-stable and dynamic electrochemicaltransistor devices, will now be exemplified along with reference tofigures thereof and an outline of their working principles.

[0064] Bi-stable Transistor (Type 1): FIGS. 1A and 1B schematically showone embodiment of the present invention, wherein a bi-stable transistoris employed. The transistor comprises a source contact 1, a draincontact 2 and an electrochemically active element 3, which have all beenformed from a continuous piece of organic material. The source contact 1is in direct electrical contact with the first pad 8′ of the antennamember, and the drain contact 2 is in direct electrical contact with thesecond pad 8″ of the antenna member. Both the source and drain contactsare in electrical contact with an external power source, which allowsthe application of a voltage V_(ds) between them. The transistor furthercomprises a gate electrode 4, which can be formed from the same organicmaterial as the source and drain contacts and the electrochemicallyactive element. The gate electrode 4 is in electrical contact with anexternal power source, which allows applying a voltage V_(g) between thegate electrode and the electrochemically active element. This can berealised by applying V_(g) between the gate 4 and the source 1 or thedrain 2, or directly between the gate 4 and the electrochemically activeelement 3. All of these organic material components have been depositedin one layer on a support 6. On top of this layer, covering part of thegate electrode 4 and the active element 3, is a layer of gel electrolyte5. Furthermore, the gel electrolyte layer 5 is covered with anencapsulating layer 7 for prevention of solvent evaporation.

[0065] Working principle for the polarity of V_(g) shown in FIG. 1, andin the case of an organic material which is conducting in its oxidisedstate and non-conducting when reduced to its neutral state: when a gatevoltage V_(g) is applied between the gate electrode 4 and theelectrochemically active element 3, the gate electrode is polarisedpositive (anode), and the electrochemically active element is polarisednegative (cathode). This leads to onset of electrochemistry in theelectrochemically active element and at the gate electrode; the organicmaterial in the transistor channel is reduced at the same time as anoxidation reaction takes place at the gate electrode. The reducedmaterial in the transistor channel displays a drastically diminishedelectrical conductivity, which results in the closure of the transistorchannel and an effective reduction of the current between source anddrain for a given source-drain voltage V_(ds), i.e. the transistor is inan “off” mode. When the external circuit supplying voltage to the gateelectrode and the electrochemically active element is broken, theoxidation state of the transistor channel is maintained. No reversal ofthe electrochemical reactions is possible because of the interruption byelectrolyte 5 of electron flow between gate electrode 4 andelectrochemically active element 3.

[0066] Thus, the bi-stable transistor has a memory-function: It ispossible to switch on or off the transistor channel with short pulses ofgate voltage, V_(g), applied to the gate. The respective conductivitystates remain when gate voltage is removed (a zero-power device).Further adjustments of conduction characteristics in theelectrochemically active element, or resetting thereof to the initial,high conductivity mode, can be performed by applying different voltagesto the gate electrode.

[0067] Consequently, by operating the transistor member of the device,the characteristics of the antenna member can be controlled.

[0068]FIG. 1C shows an alternative embodiment, wherein the secondantenna pad is omitted and the drain of the transistor member isconnected directly to ground potential.

[0069] Dynamic Transistor: FIGS. 2A and 2B schematically show a deviceaccording to the invention employing a dynamic transistor. Thetransistor comprises a source contact 1, a drain contact 2 and anelectrochemically active element 3, which have all been formed from acontinuous piece of organic material. The source contact 1 is in directelectrical contact with the first pad 8′ of the antenna member, and thedrain contact 2 is in direct electrical contact with the second pad 8″of the antenna member. The electrochemically active element 3 comprisesa transistor channel 3 a and a redox sink volume 3 b. Both the sourceand drain contacts are in electrical contact with an external powersource, which allows the application of a voltage V_(ds), between them.The transistor further comprises two gate electrodes 4 a and 4 barranged on either side of the electrochemically active element 3. Thegate electrodes can be formed from the same organic material as thesource and drain contacts and the electrochemically active element. Thegate electrodes are in electrical contact with an external power source,which allows application of a voltage V_(g) between them. All of theseorganic material components have been deposited in one layer on asupport 6. On top of this layer, covering parts of the gate electrodes 4a and 4 b and the active element 3, is a layer of gel electrolyte 5.Furthermore, the gel electrolyte layer 5 is covered with anencapsulating layer 7 for prevention of solvent evaporation.

[0070] Working principle for the polarity of V_(g) shown in FIG. 2, andin the case of an organic material which is conducting in its oxidisedstate and non-conducting when reduced to its neutral state: when a gatevoltage V_(g) is applied between the gate electrodes 4 a and 4 b, gateelectrode 4 a is polarised positive (anode), and gate electrode 4 b ispolarised negative (cathode). This leads to onset of electrochemistry inthe electrochemically active element; the organic material in thetransistor channel 3 a (adjacent to gate electrode 4 a) is reduced,while the organic material in the redox sink volume 3 b (adjacent togate electrode 4 b) is oxidised. These electrochemical reactions requirean internal transfer of electrons within the electrochemically activeelement. Electrons that are released in the oxidation reaction in theredox sink volume migrate to the transistor channel, where theyreplenish the electrons consumed in the reduction of organic materialoccurring in this segment of the electrochemically active element. Thereduced volume in the transistor channel displays a drasticallydiminished electrical conductivity, which results in the closure of thetransistor channel and an effective reduction of the source-draincurrent for a given source drain voltage V_(ds), i e the transistor is“off”. When the external circuit applying voltage to the gate electrodes4 a and 4 b is broken, a spontaneous discharge occurs, in that electronsflow from the reduced material in the transistor channel to the oxidisedmaterial in the redox sink volume, until the original redox state isre-established within the electrochemically active element. Formaintenance of overall charge neutrality, this flow of electrons withinthe electrochemically active element is accompanied by an ion flowwithin the solidified electrolyte.

[0071]FIG. 2C shows an alternative embodiment, wherein the secondantenna pad is omitted and the drain of the transistor member isconnected directly to ground potential.

[0072] Bi-stable Transistor (Type 2): FIGS. 3A and 3B schematically showanother embodiment of the present invention employing a bi-stabletransistor, the architecture of which is based on the dynamic transistorarchitecture described above. With reference to FIGS. 3A and 3B, thisembodiment of a bi-stable transistor has the same components as saiddynamic transistor, the difference being that the layer of solidifiedelectrolyte 5 is patterned, forming two separate segments of electrolyte5 a and 5 b. This patterning has the effect of interrupting ion flowwithin the electrolyte, which interruption in turn means that nospontaneous reversal of electrochemical reactions can occur betweentransistor channel 3 a and redox sink volume 3 b. In similarity to thecase of the first bi-stable transistor device described above, theoxidation state of the transistor channel is maintained when theexternal circuit, here supplying voltage to the gate electrodes, isbroken.

[0073]FIG. 3C shows an alternative embodiment, wherein the secondantenna pad is omitted and the drain of the transistor member isconnected directly to ground potential.

[0074] Experiments

[0075] The antenna pads and the Bi-stable (type 1) transistors wererealised by patterning films of partially oxidisedpoly(3,4-ethylenedioxythiophene) with poly(styrene sulphonate) ascounterions (frequently referred to as PEDOT:PSS in the present text)into a T-shaped structure with one antenna pad connected to the sourceelectrode and the other antenna pad connected to the gate electrode. Theantenna pads were also patterned from the same films of partiallyoxidised poly(3,4-ethylenedioxythiophene) with poly(styrene sulphonate)as counterions. The design followed the schematic drawings of thebi-stable transistor in combination with two antenna pads presented inFIG. 1. In its pristine, partially oxidised state, PEDOT:PSS films areconductive, providing the opportunity of modulating the current in thetransistor channel, between the two antenna pads, by reduction andoxidation of the PEDOT:PSS electrochemically. All processing andmaterial handling was done in ambient atmosphere.

[0076] Patterning through Screen-printing: PEDOT:PSS was applied as athin film on a polyester carrier, Orgacon™ EL-300Ω/square, as providedby AGFA. Conducting patterns were generated using a screen-printeddeactivation paste: Orgacon-Strupas gel, as provided by AGFA, was mixedwith an aqueous sodium hypochlorite solution, resulting in aconcentration of the active degradation agent of approximately 1.2%.Printing was performed using a manual screen printing board (Movivis,purchased from Schneidler) using a screen with 77 lines/cm mesh. After 1minute, the deactivation agent was removed from the PEDOT:PSS film bywashing thoroughly with copious amounts of water.

[0077] Deposition of Gate Electrode(s): After patterning of thePEDOT:PSS film, silver-paste (DU PONT 5000 Conductor) was printed on topof the PEDOT:PSS areas that form the gate electrode(s). Alternatively,the transistor part can be entirely made of organic materials by locallyincreasing the layer thickness of the PEDOT:PSS in the gate area(s) bydrying-in of a PEDOT-PSS solution (Baytron P™ from Bayer) onto theseareas. Such all-organic transistor members were successfully realised onpolyester foils.

[0078] Deposition of Gelled Electrolyte: Calcium chloride (2%),iso-propanol (35%), and gelatine (10%) (Extraco gelatine powder 719-30)were dissolved in de-ionised water at approximately 50° C. (weightpercentages of the resulting gel in parenthesis). Structures of gelledelectrolyte on patterned PEDOT:PSS film were formed by printing the gelon top of the PEDOT:PSS film. The thickness of the gelled electrolyteranged from 20 to 100 μm. Gelled electrolyte structures were realised atline widths down to 300 μm. Screen-printing of gelled electrolyte wasperformed using a 32 mesh screen.

[0079] Encapsulation: The gelled electrolyte was coated with awaterproof coating, such as plastic paint or foils, encapsulating thedevice. Shelf lifetimes of several months were achieved.

[0080] Electrical Characterisation: All testing was performed in ambientatmosphere at room temperature. The transmitter/reader part consisted ofa spectrum analyser and an inductor connected in parallel with the twoantenna pads. Changes in the capacitive coupling to the electrochemicaldevice according to the invention (a transponder) was then detected asan altered resonance frequency of the circuit.

[0081] Results

[0082] Two Antenna Pads Connected to Source and Drain Respectively of aBi-stable Transistor: A bi-stable transistor in combination with antennapads such as that shown schematically in FIGS. 1A and 1B was realised.The transistor member of the device according to the invention had atransistor channel width of 5 mm and a gel width of 5 mm, with atransistor channel of 0.25 cm². However, smaller dimensions can berealised by using photolithographic photoresist patterning incombination with reactive ion plasma etching. Channel widths rangingfrom 5 to 20 μm and gel width of 20 μm can be realised.

[0083] The gate voltages V_(g) applied to the gate electrode were in theinterval between 0 V and 0.7 V in the reader signals are shown in FIG.4.

[0084] Two Antenna Pads Connected to Source and Drain Respectively of aDynamic Transistor: A dynamic transistor with two antenna pads connectedto source and drain of a bi-stable transistor respectively, such as thatshown schematically in FIGS. 2A and 2B was realised. The dynamictransistor had a channel width of 5 mm and a gel width of 5 mm, with atransistor channel of 0.25 cm². Smaller dimensions of PEDOT and gelpatterns down to 4 μm can be reached using photolitographic patterning.Channel widths ranging from 4 to 20 μm and a gel width of 20 μm can thusbe realised.

[0085] Typically, the gate voltages V_(g) applied to the gate electrodesspanned an interval of 0 V to 3 V. FIG. 5 displays the reader outputcharacteristics for different gate voltages applied (0 and 3 V).

[0086] The principle behind the read-out of the inventive device isschematically shown in FIG. 6. The antenna member along with thetransistor member of the electrochemical device is outlined in the rightportion 61 of FIG. 6, wherein the controllable resistance or impedancebetween the antenna pads is indicated as a variable resistor/impedance63. It is to be understood that this variable resistor/impedance is, infact, the transistor member of the device. The left portion 62 of FIG. 6shows a read-out device, comprising a voltage supply and an LC-circuit.Furthermore, the read-out device comprises a receiver unit (not shown)for detection of the response from the electrochemical device accordingto the invention. When the read-out device is used for reading anelectrochemical device, it is brought into capacitive contact with thesame. In the figure, this is indicated by capacitors 65 between theread-out device 62 and the electrochemical device 61. It is to beunderstood that the read-out device may have a similar configuration tothe electrochemical device.

[0087]FIG. 7 shows a similar situation as in FIG. 6, wherein the drainof the transistor member is now connected to ground potential. In thiscase, the read-out device is also connected to ground potential, asshown.

[0088] In FIG. 8, response curves for different gate voltages are shownfor a bi-stable transistor member. As shown in the figure, the frequencyresponse is dependent on the applied gate voltage (0 V and 5 V,respectively). Hence, a change in the state of the transistor member ofthe inventive electrochemical device can be read remotely by means ofthis frequency shift in the response curve. In this way, an ID-code maybe remotely read from the electrochemical device according to theinvention by means of a read-out device that is capacitively coupled tothe antenna member. As seen, the frequency response of the device is ata higher frequency when the transistor is in an isolating state, than ina conducting state.

[0089]FIG. 9 shows a similar situation as FIG. 8, but in the case of adynamic transistor member. Again, and as seen from the figure, thefrequency response of the device is at a higher frequency when thetransistor is in an isolating state, than in a conducting state.

[0090] It is also conceivable that the state of the transistor member isaltered by environmental influence, thereby, in fact, making the devicea remotely readable sensor. For example, the characteristics of theelectrolyte may change according to temperature, humidity or some otherinfluence, such that the frequency response is altered.

[0091] In conclusion, a transmitter device based on electrochemicaltransistors connected to an antenna member has been disclosed. A firstpad of the antenna member is connected to the source of a transistor,and a second pad of the antenna member is connected to the drain of thetransistor. The charge transport between the two pads is controlled bythe transistor member of the inventive device.

1. A supported or self-supporting electrochemical device comprising: (i)a transistor member having a source contact, a drain contact, at leastone gate electrode, an electrochemically active element arrangedbetween, and in direct electrical contact with, the source and draincontacts, which electrochemically active element comprises a transistorchannel and is of a material comprising an organic material having theability of electrochemically altering its conductivity through change ofredox state thereof, and a solidified electrolyte in direct electricalcontact with the electrochemically active element and said at least onegate electrode and interposed between them in such a way that electronflow between the electrochemically active element and said gateelectrode(s) is prevented, whereby flow of electrons between sourcecontact and drain contact is controllable by means of a voltage appliedto said gate electrode(s); and (ii) an antenna member having a firstantenna pad and a second antenna pad, said first antenna pad being indirect electrical contact with the source of the transistor member, andsaid second antenna pad being in direct electrical contact with thedrain of the transistor member.
 2. An electrochemical device accordingto claim 1, in which said source and drain contacts, gate electrode(s)and electrochemically active element are arranged in one common plane.3. An electrochemical device according to claim 2, in which a continuousor interrupted layer of said solidified electrolyte covers theelectrochemically active element and covers at least partially said gateelectrode(s).
 4. An electrochemical device according to claim 1, inwhich at least one of said antenna pads, source and drain contacts andgate electrode(s) is formed from the same material as theelectrochemically active element.
 5. An electrochemical device accordingto claim 4, in which all of said antenna pads, source and drain contactsand gate electrode(s) are formed from the same material as theelectrochemically active element.
 6. An electrochemical device accordingto claim 4, in which the antenna pads, source and drain contacts and theelectrochemically active element are formed from a continuous piece ofsaid material comprising an organic material.
 7. An electrochemicaldevice according to claim 1, in which said transistor channel retainsits redox state upon removal of the gate voltage.
 8. An electrochemicaldevice according to claim 1, in which said transistor channelspontaneously returns to its initial redox state upon removal of thegate voltage.
 9. An electrochemical device according to claim 8, inwhich the electrochemically active element further comprises a redoxsink volume adjacent to the transistor channel, the device comprising atleast two gate electrodes arranged on opposite sides of theelectrochemically active element so that one gate electrode is closer tothe transistor channel and one gate electrode is closer to the redoxsink volume.
 10. An electrochemical device according to claim 1, inwhich said organic material is a polymer.
 11. An electrochemical deviceaccording to claim 10, in which said polymer material is selected fromthe group consisting of polythiophenes, polypyrroles, polyanilines,polyisothianaphtalenes, polyphenylene vinylenes and copolymers thereof.12. An electrochemical device according to claim 11, in which saidpolymer material is a polymer or copolymer of a 3,4-dialkoxythiophene,in which said two alkoxy groups may be the same or different or togetherrepresent an optionally substituted oxy-alkylene-oxy bridge.
 13. Anelectrochemical device according to claim 12, in which said polymer orcopolymer of a 3,4-dialkoxythiophene is selected from the groupconsisting of poly(3,4-methylenedioxythiophene),poly(3,4-methylenedioxythiophene) derivatives,poly(3,4-ethylenedioxythiophene), poly(3,4-ethylenedioxythiophene)derivatives, poly(3,4-propylenedioxythiophene),poly(3,4-propylenedioxythiophene) derivatives,poly(3,4-butylenedioxythiophene), poly(3,4-butylenedioxythiophene)derivatives, and copolymers therewith.
 14. An electrochemical deviceaccording to claim 1, in which said organic material further comprises apolyanion compound.
 15. An electrochemical device according to claim 14,in which said polyanion compound is poly(styrene sulphonic acid) or asalt thereof.
 16. An electrochemical device according to claim 1, inwhich said solidified electrolyte comprises a binder.
 17. Anelectrochemical device according to claim 16, in which said binder is agelling agent selected from the group consisting of gelatine, a gelatinederivative, polyacrylic acid, polymethacrylic acid,poly(vinylpyrrolidone), polysaccharides, polyacrylamides, polyurethanes,polypropylene oxides, polyethylene oxides, poly(styrene sulphonic acid)and poly(vinyl alcohol), and salts and copolymers thereof.
 18. Anelectrochemical device according to claim 1, in which said solidifiedelectrolyte comprises an ionic salt.
 19. An electrochemical deviceaccording to claim 1, which is self-supporting.
 20. An electrochemicaldevice according to claim 1, which is arranged on a support.
 21. Anelectrochemical transistor device according to claim 20, in which saidsupport is selected from the group consisting of polyethyleneterephthalate, polyethylene naphthalene dicarboxylate, polyethylene,polypropylene, polycarbonate, paper, coated paper, resin-coated paper,paper laminates, paperboard, corrugated board and glass.
 22. A supportedor self-supporting electrochemical device comprising: (i) anelectrochemical transistor member having a source contact, a draincontact, at least one gate electrode, an electrochemically activeelement arranged between, and in direct electrical contact with, thesource and drain contacts, which electrochemically active elementcomprises a transistor channel and is of a material comprising anorganic material having the ability of electrochemically altering itsconductivity through change of redox state thereof, and a solidifiedelectrolyte in direct electrical contact with the electrochemicallyactive element and said at least one gate electrode and interposedbetween them in such a way that electron flow between theelectrochemically active element and said gate electrode(s) isprevented, whereby flow of electrons between source contact and draincontact is controllable by means of a voltage applied to said gateelectrode(s); and (ii) an antenna member having an antenna pad, saidantenna pad being in direct electrical contact with the source of saidtransistor member, said drain of said transistor member beingelectrically connected to ground.
 23. A process for manufacturing of anelectrochemical device as defined in claim 1, wherein said antennapad(s), contacts, electrode(s), electrochemically active element and/orelectrolyte are deposited by means of printing techniques.
 24. A processaccording to claim 23, wherein said antenna pad(s), contacts,electrode(s), electrochemically active element and electrolyte aredeposited by means of coating techniques.
 25. A process according toclaim 23, in which device said organic material comprises a polymer,which process comprises deposition of said polymer on a support throughin situ polymerisation.
 26. A process according to claim 23, comprisingpatterning of any one of said contacts, electrode(s) andelectrochemically active element using a subtractive method.
 27. Aprocess according to claim 26, in which said patterning is performedthrough chemical etching.
 28. A process according to claim 26, in whichsaid patterning is performed through gas etching.
 29. A processaccording to claim 26, in which said patterning is performed bymechanical means, comprising scratching, scoring, scraping and milling.30. An electrochemical device according to claim 5, in which the antennapads, source and drain contacts and the electrochemically active elementare formed from a continuous piece of said material comprising anorganic material.
 31. A process according to claim 24, in which devicesaid organic material comprises a polymer, which process comprisesdeposition of said polymer on a support through in situ polymerisation.32. A process according to claim 24, comprising patterning of any one ofsaid contacts, electrode(s) and electrochemically active element using asubtractive method.
 33. A process according to claim 25, comprisingpatterning of any one of said contacts, electrode(s) andelectrochemically active element using a subtractive method.